1. Field of the Invention
The present invention relates to a vehicle seat. More specifically, the present invention relates to a vehicle seat having a rotatable backrest which can be solely rotated on a seat cushion when the vehicle is in reverse, when baggage is loaded on and off a rear seat from a front seat, or when the vehicle is cornering, for example.
2. Description of the Related Art
A conventional vehicle seat comprises a seat cushion upon which a driver or other passengers are seated and a backrest to support the back of the driver or other passengers, which backrest is tiltably supported at the seat cushion through a reclining adjusting mechanism. The seat cushion is slidable and can be moved back and forth relative to the floor of the vehicle. These mechanisms allow the driver to assume the most comfortable position and a passenger access to the rear seat by folding the backrest forward in the case of a two door automobile. Also, the driver can reach the rear seat by folding the backrest backward.
Proposals have been made, but not generally practiced, to provide a rotatable vehicle seat in which the seat cushion is rotatably mounted on the floor of the vehicle to make it easier to enter and exit from the vehicle (c.f., for example, U.S. Pat. Nos. 2,290,464, 2,587,679, and 4,600,239). In this case, the seat cushion must be immovably locked to the floor after the driver or other passenger is seated. In such a conventional vehicle seat, the backrest rotates together with the seat cushion, and it is impossible to rotate the backrest alone, relative to the seat cushion, about a vertical axis.
Of course, many rotatable seats and chairs for other purposes are known. For example, Japanese Unexamined Utility Model Publication (Kokai) No. 61-18051 discloses a Japanese type chair with a rotatable backrest.
Many advantages may be gained if a vehicle seat can be rotated about a vertical axis, such as when entering and exiting from the vehicle and when loading and unloading baggage from the rear seat while the driver is sitting on the front seat, as stated above. Further, it would be advantageous if the vehicle seat could rotate about the vertical axis during a certain running state of the vehicle. For example, the driver will be able to obtain a better and more comfortable view through the rear window when the vehicle is reversing, if the backrest is rotatable. However, the internal space of the vehicle is usually very restricted, and it is very difficult to arrange a vehicle seat rotatable about a vertical axis, with the exception of custom-built vehicles.
It will be almost impossible to directly mount an existing chair, for example, a chair with a rotatable backrest as disclosed in the above-described Kokai No. 61-18051 in the vehicle, for if such a seat with a freely rotatable backrest is mounted in a vehicle, problems will arise wherein the driver's position becomes unstable during a running state of the vehicle because the backrest can move freely and the driver's body will be allowed to turn when the vehicle is cornering.